Steam turbine nozzle plate having 360 discharge

ABSTRACT

An inner shell of a steam turbine has discrete arcuate steam outlet ports through an axial face. In axial opposition is a nozzle ring including a pair of nozzle ring segments joined at a horizontal midline. At the midline joint, split partitions are employed to provide a full 360° discharge through the nozzle ring. The split partitions are split in an axial direction to define discrete partition portions in each of the nozzle ring segments adjacent the midline joint.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a steam turbine nozzle plate fordischarging steam received from discrete supply ports of the turbineinner shell in a continuous uninterrupted 360° arc and particularlyrelates to a steam turbine nozzle plate having split partitions at thehorizontal midline of the turbine for eliminating flow restrictions orblockages typical of prior nozzle designs at the horizontal midline.

[0002] In a typical steam turbine, an inner shell is provided having,e.g., four inlet ports for receiving steam in directions generallynormal to the axis of the turbine. Conventionally, a pair of valvedinlet ports are provided on the upper half of the inner shell and asimilar pair of valved inlet ports are provided on the lower half of theinner shell. These discrete steam flow passages turn the steam from aflow direction generally normal to the axis of the turbine into aunidirectional axial flow for flow through associated discrete steamoutlet ports in an end axial face of the inner shell. These discreteoutlet ports are arcuate and are spaced one from the other by bridgingportions. For example, at the horizontal midline of the steam turbine,the bridging portions define the extreme ends of the outlet ports.Similarly, bridging portions are also provided in the inner shell alongthe vertical centerline of the turbine and define the opposite extremeends of the outlet ports. It will thus be appreciated that the steamoutlet flow through the discrete ports of the inner shell enablespartial arc admissions into the nozzles of the steam turbine dependingupon the valved inlet flows and precludes a full 360° arc admission.Typically, and with all inlet valves open, a steam admission of about340° arc maximum is obtained.

[0003] The nozzles for the turbine typically include inner and outerbands with stator vanes or partitions extending in generally radialdirections between the inner and outer bands. The nozzle ring isprovided in 180° segments which are joined to one another along thehorizontal midline of the turbine. The axial inlet side of the nozzlering bears against the axial face of the inner shell such that thenozzles receive the steam flowing through the discrete outlet ports ofthe inner shell as partial arc steam admissions. Typically, the nozzlesegments, for design and other reasons, have end blocks adjacent thehorizontal midline. These end blocks have a circumferential extent whichblocks part of the admission from the axially adjoining outlet port ofthe inner shell. The nozzle segments also included port bridges whichare aligned with the vertical bridging portions of the inner shell uponassembly. As a consequence of this construction, particularly the largeend blocks at the horizontal midline of the turbine, the steam flow fromthe outlet ports of the inner shell is interrupted by the discontinuityof the end blocks. The resulting partial arc admission of steam to andthrough the nozzles has limited efforts to upgrade flow rates throughthe turbine and, hence, inhibited desired increases in efficiency.

BRIEF DESCRIPTION OF THE INVENTION

[0004] In accordance with a preferred embodiment of the presentinvention, there is provided a nozzle plate which affords increased fullload efficiency in the steam turbine through employment of a continuousuninterrupted 360° inlet nozzle design. Particularly, the nozzle plateis fabricated similarly as prior nozzle plates, preferably in 180°segments. However, the end blocks which previously occupied asubstantial circumferential extent of the nozzle plate are entirelyeliminated and partitions are provided which extend 360° about the rotoraxis without interruption from ancillary structure. More particularly, asplit partition is provided at each of the horizontal midline jointsbetween the nozzle ring segments such that steam from the outlet portsof the inner shell on opposite sides of the horizontal midline flowsalong opposite sides of the split partition. Each nozzle segment has, atthe midline joint, a partition portion which mates with anotherpartition portion of the adjacent segment upon assembly of the segmentsto form a split partition whereby steam flows from adjacent outlet portsof the inner shell along opposite sides, respectively, of the splitpartition. The partition is thus split in the axial direction of theturbine.

[0005] Additionally, a port bridge is disposed in the nozzle in front ofeach of the split partitions at the horizontal midline. The port bridgesaxially register with the bridging portions between the pairs ofadjacent outlet ports of the inner shell at opposite sides of thehorizontal midline. A weld buildup is provided between each splitpartition and its associated port bridge to form a continuous surfacefor guiding the steam flow from the inlet ports along respectiveopposite sides of the split partition. As a consequence, full 360° steamadmission is provided.

[0006] In a preferred embodiment according to the present invention,there is provided a nozzle plate for a turbine comprising nozzle platesegments forming an annular array of nozzles, each segment includinginner and outer band portions and circumferentially spaced partitionsextending between the inner and outer band portions, adjacent ends ofthe segments forming a joint therebetween, at least one of the jointsincluding a split partition with a first portion of the split partitionforming part of an end of one segment and a second portion of the splitpartition forming part of an adjacent end of another segment.

[0007] In a further preferred embodiment according to the presentinvention, there is provided a steam turbine comprising an inner shellhaving an axial face and a plurality of axially opening arcuately shapedsteam outlet ports about the face with bridging portions between theoutlet ports, a pair of the bridging portions being located at ahorizontal midline of the turbine, a plurality of nozzle segmentsforming an annular array of nozzles in axial registration with the axialfaces of the inner shell, each segment including inner and outer bandportions and circumferentially spaced partitions extending between theinner and outer band portions, adjacent ends of the segments formingjoints therebetween with a pair of the joints lying along the horizontalmidline of the turbine, the joints between the segments along thehorizontal midline lying in axial registration with bridging portions ofthe inner shell at the horizontal midline, each joint including a splitpartition with a first portion of the split partition forming part of anend of one segment and a second portion of the split partition formingpart of an end of the adjacent segment, thereby enabling steam flowthrough adjacent outlet ports on opposite sides of the horizontalmidline to in part flow along opposite sides of the split partition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a fragmentary perspective view illustrating upper andlower nozzle segments constructed in accordance with a preferredembodiment of the present invention;

[0009]FIG. 2 is an enlarged fragmentary side elevational viewillustrating the nozzle ring and inner shell;

[0010]FIG. 3 is an axial end view of the axial face of the inner shellwhich registers with the inlet side of the nozzle ring with portions ofthe nozzle plate superimposed;

[0011]FIG. 4 is a schematic fragmentary cross-sectional view of one ofthe horizontal joints of the nozzle segments in conjunction with theinlet ports, the view being folded out in plan;

[0012]FIG. 5 is a schematic illustration of the upper and lower nozzlering segments folded in plan illustrating the split partitions at thehorizontal midline; and

[0013]FIG. 6 is a fragmentary view of a nozzle segment at its horizontaljoint folded out in plan view according to the prior art illustratingthe end blockage.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Referring now to the drawings, particularly to FIGS. 1 and 2,there is schematically illustrated a portion of a diaphragm, generallydesignated 10, for use in steam turbines and includes a nozzle plate orring 12 having inner and outer bands 14 and 16, respectively. Aplurality of stator vanes or partitions 18 are spaced circumferentiallyone from the other about the nozzle ring 12 and extend generally inradial directions between the inner and outer bands 14 and 16. Asillustrated in FIG. 1, the nozzle ring is separated into preferably apair of upper and lower nozzle ring segments 20 and 22 which are joinedone to the other along the horizontal midline of the steam turbine atinstallation. As illustrated in FIG. 2, the nozzle ring 10 forms part ofthe diaphragm for receiving steam from an inner shell 24. As illustratedin FIG. 2, the partitions 18 receive steam from outlet ports, describedbelow, and discharge the steam to drive the buckets 26 of the firststage of the steam turbine rotor 28.

[0015] Referring to FIGS. 2 and 3, the inner shell 24 includes aplurality of valved steam admission ports. In the illustrated form, apair of steam inlet ports 30 are formed along the upper side of theinner shell 24, while a similar pair of valved inlet ports 30 aredisposed along the lower half of the inner shell 24. The inner shell 24includes passages 32 associated with each of the inlet ports 30 forturning the steam from an inlet direction generally normal to the axisof rotation of the turbine to an axial direction for flow through steamoutlet ports 34 in the axial face 36 in axial registration with thenozzle ring 12. From a review of FIG. 3, it will be appreciated thateach steam outlet port 34 is associated with a valved steam inlet port30 and is generally arcuate in configuration, each outlet port 34subtending an arc less than 900. Bridging portions 39 are providedadjacent steam outlet ports 34 along opposite sides of the horizontalmidline 37 and bridging portions 38 are provided along the verticalcenterline to maintain the outlet ports 34 segregated one from theother. Valved steam admission through the segregated steam outlet ports34 is useful when one or more of the valved inlet ports 30 are used tosupply steam while the other valved inlet port(s) do not supply steam.Consequently, it will be appreciated that in the illustrativeembodiment, the steam inlet ports 34 are arcuate about the rotor axis,lie in quadrants less than 90° and are separated one from the other bybridging portions 39 and 38 along the axial face of the inner shell 24.Also illustrated in FIG. 3 is a superimposition in schematic form of thenozzle ring 12 and partitions 18 illustrating their location relative tothe steam inlet ports 34.

[0016] Referring to FIG. 6, there is illustrated a portion of a priorart nozzle ring segment laid out in plan to illustrate an end blockportion 50 along the horizontal midline. Particularly as illustrated,the nozzle ring 52 includes a plurality of partitions 54 which extendgenerally radially and an end block portion 50 which extends a discretecircumferential extent. The end block 50, in combination with the endblock 50 of the opposing nozzle ring segment, as well as end blocksalong the diametrically opposite side of the nozzle ring occupycircumferential extents which otherwise could receive a number ofpartitions, e.g., five or six partitions each. It will be appreciated,however, that because of the end block portions 50, a full 360°discharge through the nozzle ring 52 cannot be achieved.

[0017] In accordance with a preferred embodiment of the presentinvention and with reference to FIGS. 4 and 5, a full 360° uninterruptedflow of steam through the nozzle ring 12 hereof is provided. Toaccomplish this, the end block typically provided on each of the upperand lower nozzle segments adjacent each of the midline joints isentirely eliminated and replaced by a number of additional partitionsand a split partition. Particularly, the partitions 18 are provided inthe areas adjacent the midline joints of the nozzle segments, a splitpartition 60 being provided at each of the midline joints. Moreparticularly, the split partition 60 includes along one midline joint ofone of the nozzle ring segments a suction side partition portion 62. Theadjacent segment of the nozzle ring segment includes a pressure sideportion 64 of the split partition 60. The split partition portions, uponassembly, are joined one to the other along an axially extending splitline 66, e.g., by welding. It will be appreciated that the number ofpartitions 18 illustrated in FIGS. 4 and 5 are reduced from the actualnumber of partitions for clarity.

[0018] For example, as illustrated in FIG. 4, the upper nozzle ringsegment 20 includes a suction side partition portion 62 along one endthereof and a pressure side partition portion 64 along its opposite end.The lower nozzle ring segment 22 includes a suction side partitionportion 62 and a pressure side partition portion 64 adjacent oppositeends. When the upper and lower segments 20 and 22 are assembled, thesuction and pressure side portions 62 and 64, respectively, mate withone another to form a single complete partition 60. The partition 60 isspaced from and configured similarly as the adjacent partitions 18 aboutthe nozzle ring.

[0019] As illustrated in FIGS. 4 and 5, the leading edges of thepartitions 18 are axially inset from the leading edge of the nozzlediaphragm. Additionally, strength bridges 68 are disposed between theinner and outer rings at periodic circumferentially spaced positionsforwardly of the partitions 18. As best illustrated in FIG. 4, it willbe appreciated that each of the horizontal joints between the upper andlower nozzle ring segments 20 and 22, respectively, lie in axialregistration with the bridging portions 36 of the inner shell 24 at thehorizontal midline 37. To provide strength to the nozzle ring andcontinuous flow of steam along opposite sides of each split partition 60from the adjacent steam outlet ports 34, a port bridge 70 extendsbetween the inner and outer rings forwardly of the leading edge of thesplit partition 60. Additionally, a weld buildup 72 is provided betweenthe port bridge 70 and the split partition 60 to form the continuoussurface along opposite sides of the split partition. Similarly, at thevertical centerlines of the nozzle segments in axial opposition to thebridging portions 38 between the steam outlet ports 34 of the innershell, port bridges 74 are provided (FIG. 5). By providing the portbridges 70 and 74, partial arc admissions of steam may be provided fromone or more of the valved inlet ports 30. It will be appreciated,however, that when steam is provided through each of the valved inletports 30 for flow through the outlet ports 34, the nozzle ring providesa full 3600 discharge of steam onto the buckets of that stage.

[0020] While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A nozzle plate for a turbine comprising: nozzle plate segments forming an annular array of nozzles, each segment including inner and outer band portions and circumferentially spaced partitions extending between said inner and outer band portions, adjacent ends of said segments forming a joint therebetween; at least one of said joints including a split partition with a first portion of the split partition forming part of an end of one segment and a second portion of the split partition forming part of an adjacent end of another segment.
 2. A nozzle plate according to claim 1 including a port bridge disposed in front of said split partition.
 3. A nozzle plate according to claim 1 wherein each of said segments subtends an arc of 180°, another of said joints between said segments including a second split partition with a first portion thereof forming part of an end of said one segment and a second portion thereof forming part of an adjacent end of said another segment.
 4. A nozzle plate according to claim 3 including a port bridge disposed between said inner and outer bands in an upstream direction relative to said split partitions.
 5. A nozzle plate according to claim 1 wherein the split partition is split in an axial direction.
 6. A nozzle plate according to claim 1 wherein each of said segments subtends an arc of 180°, another of said joints between said segments including a second partition split in an axial direction with a first portion thereof forming part of an end of said one segment and a second portion thereof forming part of an adjacent end of said another segment, said split partitions being split in axial directions.
 7. A nozzle plate according to claim 1 wherein each of said segments subtends an arc of 180°, another of said joints between said segments including a second partition split in an axial direction with a first portion thereof forming part of an end of said one segment and a second portion thereof forming part of an adjacent end of said another segment, including a port bridge disposed in front of each said split partition, and a weld buildup between a leading edge of each split partition and the port bridge.
 8. A steam turbine comprising: an inner shell having an axial face and a plurality of axially opening arcuately shaped steam outlet ports about said face with bridging portions between said outlet ports, a pair of said bridging portions being located at a horizontal midline of the turbine; a plurality of nozzle segments forming an annular array of nozzles in axial registration with said axial faces of said inner shell, each segment including inner and outer band portions and circumferentially spaced partitions extending between said inner and outer band portions, adjacent ends of said segments forming joints therebetween with a pair of said joints lying along said horizontal midline of the turbine; the joints between said segments along said horizontal midline lying in axial registration with bridging portions of the inner shell at said horizontal midline, each joint including a split partition with a first portion of the split partition forming part of an end of one segment and a second portion of the split partition forming part of an end of the adjacent segment, thereby enabling steam flow through adjacent outlet ports on opposite sides of the horizontal midline to in part flow along opposite sides of said split partition.
 9. A turbine according to claim 8 including a port bridge disposed in front of each said split partition.
 10. A turbine according to claim 8 wherein each of said segments subtends an arc of 180°.
 11. A turbine according to claim 8 including a port bridge disposed in front of each said split partition, and a weld buildup between a leading edge of each split partition and the port bridge.
 12. A turbine according to claim 8 wherein each of said split partitions are split in an axial direction.
 13. A turbine according to claim 12 including a port bridge disposed in front of each said split partition, and a weld buildup between a leading edge of each split partition and the port bridge. 